Transparent conductive oxide films have low resistance and relatively high transmittance in the region of visible light. For this reason, these transparent conductive oxide films are used for electrodes for liquid crystal displaying elements and a variety of light receiving elements in solar cells, for example. The transparent conductive oxide films are also used in various fields such as heat ray reflective films or antistatic films for automobiles and construction materials or transparent heating bodies for preventing fogging of freezing display cases. Among these, indium oxide films to which tin is added are widely used as ITO films.
In recent years, a technique of reducing light absorption properties has become extremely important as a means for exploiting the full potential of the properties of the elements. Particularly, in applications for which the optical properties are important, such as the electrode for the liquid crystal displaying element and the electrode for a variety of light receiving elements in the solar cell, an electrode having lower light absorption properties over a wide region of wavelength is demanded.
In the ITO film above, adjustment of the light absorption properties has been attempted by adjusting the amount of tin to be added. However, it is difficult to improve both resistance and light absorption properties by this method. For example, Non Patent Literature 1 discloses dependency of electro-optical properties of a transparent conductive In2O3—SnO2 film on the amount of SnO2. According to this, the resistance of the transparent conductive In2O3—SnO2 film is the lowest at an amount of SnO2 of approximately 10 wt %. However, at such an amount of SnO2, the plasma wavelength shifts to a shorter wavelength side, increasing absorptivity in the infrared region.
On the other hand, there is an attempt to attain desired properties by adding an element to indium oxide. For example, Patent Literature 1 discloses an oxide sintered body including indium, at least one element selected from a plurality of metal elements, and oxygen, wherein the content of the selected metal element is 2.0 to 40 at %. In Patent Literature 1, examples of the plurality of metal elements include zirconium and yttrium together with other elements. However, Patent Literature 1 only discloses the oxide sintered body to which the above metal element was added singly. Patent Literature 1 only discloses a composition having a ratio of zirconium of 16.9 at % and a composition having a ratio of yttrium of 17.4 at %.